ssheets

iTrader: (1)

I posted in the right spot, but that sticky has been there for so long I don't think anbody notices
CR thread See post #88 please.


Here's the meat of it:

using a .052 graphite gasket gives these results:
72.27cc = 9.76 CR
71.71cc = 9.82 CR
71.05cc = 9.90 CR
70.59cc = 9.95 CR
70.03cc = 10.01 CR
69.74cc = 10.04 CR
68.91cc = 10.14 CR
68.35cc = 10.21 CR
67.79cc = 10.27 CR
67.23cc = 10.34 CR
66.67cc = 10.41 CR (stock LS1 head spec) ?
66.11cc = 10.48 CR
65.55cc = 10.55 CR
64.99cc = 10.63 CR
64.43cc = 10.70 CR (stock LS6 head spec)
63.87cc = 10.78 CR
63.31cc = 10.85 CR
62.75cc = 10.93 CR
62.19cc = 11.01 CR <<<I want to be here
61.63cc = 11.09 CR
61.07cc = 11.17 CR
60.51cc = 11.25 CR
59.95cc = 11.33 CR
59.39cc = 11.42 CR
58.83cc = 11.51 CR
58.27cc = 11.59 CR

If the piston is shoved back into the head to +.005 Piston Down Bore that gives a deck volume of .98cc. If an MLS gasket is used with this parameter changed the results are as follows:

72.27cc = 9.34 CR
71.71cc = 9.39 CR
71.05cc = 9.46 CR
70.59cc = 9.50 CR
70.03cc = 9.56 CR
69.74cc = 9.59 CR
68.91cc = 9.68 CR
68.35cc = 9.74 CR
67.79cc = 9.80 CR
67.23cc = 9.86 CR
66.67cc = 9.92 CR (stock LS1 head spec)
66.11cc = 9.99 CR
65.55cc = 10.05 CR
64.99cc = 10.12 CR
64.43cc = 10.18 CR (stock LS6 head spec)
63.87cc = 10.25 CR
63.31cc = 10.32 CR
62.75cc = 10.39 CR
62.19cc = 10.46 CR
61.63cc = 10.53 CR
61.07cc = 10.60 CR
60.51cc = 10.67 CR
59.95cc = 10.75 CR
59.39cc = 10.82 CR
58.83cc = 10.90 CR
58.27cc = 10.98 CR

If the piston is shoved back into the head to +.005 Piston Down Bore that gives a deck volume of .98cc. If a graphite gasket is used with this parameter changed the results are as follows:

72.27cc = 9.49 CR
71.71cc = 9.55 CR
71.05cc = 9.62 CR
70.59cc = 9.67 CR
70.03cc = 9.73 CR
69.74cc = 9.76 CR
68.91cc = 9.85 CR
68.35cc = 9.91 CR
67.79cc = 9.98 CR
67.23cc = 10.04 CR
66.67cc = 10.10 CR (stock LS1 head spec)
66.11cc = 10.17 CR
65.55cc = 10.24 CR
64.99cc = 10.30 CR
64.43cc = 10.37 CR (stock LS6 head spec)
63.87cc = 10.44 CR
63.31cc = 10.51 CR
62.75cc = 10.59 CR
62.19cc = 10.66 CR
61.63cc = 10.73 CR
61.07cc = 10.81 CR
60.51cc = 10.89 CR
59.95cc = 10.96 CR
59.39cc = 11.04 CR
58.83cc = 11.12 CR
58.27cc = 11.20 CR

There are other factors that change CR but they are relatively minor compared to these variables. I am by no means discrediting the work done by Tin Indian or even contesting the published figures. I just took the tables and extrapolated them with different variables other than stock for cc volume and swept cylinder volume. What appears to me, if I am to justify GM's published CR specs for LS1 and LS6 engines are as follows. LS1 uses 66.67cc combustion chambers, .052 gasket thickness, and a Piston Down Bore @ TDC of +.005". An LS6 engine uses a combustion chamber of 64.43cc, .060 gasket thickness, and a Piston Down Bore @ TDC of -.008". Does this point to a design difference between the LS6 block and the LS1 block I am not aware of? It would be nice to know the spec for LS1 and LS6 deck volume. I personally have a 99 LS1 that is clearly and old-style LS1 block. Are my pistons sticking up out of the hole .008 or are the down the hole .005? This makes a huge difference is computed CR and it would be a great help to the guys changing heads and getting them shaved to know this.



Somebody prove me right or wrong. I've got a stock 02 LS1 bottom end, pistons etc. I'm swapping heads using a set of 5.3's. Our desired CR is 11:1 + So using a stock MLS .052" gasket we should chamber the heads to be 62.19ccs.

Would I be better going for a tighter quinch and using a .042" gasket and going for 62.29cc Chambers?

Or how about staying with 62.19cc and measuring PtoV prior to install and if I can run the .042" and have a slightly higher CR?

I'll be installing an F14 cam and the heads have 2.02" intakes so I'll be measuring PtoV regardless

SStrokerAce

iTrader: (2)

Yes....

A good compression ratio calculator will get you all the answers you need.

Bret

PREDATOR-Z

Here try this:
http://www.c5frc.com/calculators/Com...Calculator.htm

I came up with 61.3 cc with a .042 gasket for an 11:1 (deck height at .005)

ssheets

iTrader: (1)

Can I count on stock deck height to be .005"?

JZ'sTA

iTrader: (23)

I thik most use .007 or .008

ssheets

iTrader: (1)

Predator, Nice tool. Thanks.

Next question.

I know there is a variety of gaskets out there, but without getting into ultra expensive Cometics what are my most likely options?

I'm using 5.3 heads, but they are not the notched ones and will take the stock 5.7 gaskets or ????

My goal is a 61cc chamber with a .042" gasket. If this sounds right, who's .042" gasket should I use?

Now with the F14 cam and 2.02" valves I won't be ordering gaskets until I can assemble everything and get some real measurements.

ssheets

iTrader: (1)

Well according to this calc tool to get 11:1cr I need to be 61cc for a .042" gasket and 59cc for the .052" gasket.

Sooo if I go 60cc I can measure PtoV and if posisble run the .042" gasket at 11.2:1cr or live at 10.9:1 with the .052" gasket. Looks like a good target??? (I left deck height at .008)

How likely am I to run into major problems with 2.02"intakes running an f14 cam on 60cc 5.3 heads??